Carrier for radioactive material and improved method of making the same



June 1, 1948. 5 RQSENBLUM 2,442,617 CARRIER FOR RADIO-ACTIVE MATERIALAND iMPROVED METHOD OF MAKING THE SAME Filed Oct. 51 1942 NEGATIVE lMETAL flu METAL QMMVENTOR. BY MO CKr fl w/1A ATTORNEYS Patented June 1,1943 CARRIER FOR RADIOACTIVE MATERIAL AND IMPROVED IMETHOD OF MAKING THESAME Solomon Rosenblum, Princeton, N. 1., assignor to Cana dian Radium &Uranium Corporation,

New York, N. Y., a corporation of New York Application October 31, 1942,Serial No. 464,144

4 Claims.

My invention relates to a new and improved method of incorporatingradio-active material into a carrier, and a new and improved impregnatedcarrier of radio-active material.

The principal objects of my invention are to incorporate radio-activematerial in a carrier which is made of relatively inert material, sothat said carrier will be inert to acids and many other chemicals; toincorporate into a carrier, either pure radium, or a radium alloy or aradium compound or other radio-active material; to incorporate theradio-active material in a carrier which can be made of light-permeableor transparent material, such as glass; to concentrate the incorporatedradio-active material at or adjacent one or more free or exposedsurfaces of the carrier; and to provide a simple andimproved method forincorporating radio-active material in the carrier.

The improved article of manufacture is not limited to any method ofmaking the same.

Other objects of the invention will be stated in the annexed descriptionand drawing which illustrates a preferred embodiment thereof.

The drawing is a diagrammatic view which illustrates the method ofincorporating the radioactive material into the carrier.

As an example, the carrier 3 is made of insulating material, whoseresistance decreases with a rise in temperature. While the invention gensalts of silver and of thallium, and cuprous halogen salts. I can alsouse certain natural minerals, such as calcite and witherite. Calcite orcalcspar is a common natural form of calcium carbonate, which is foundin natural crystalline form. Witherite is a natural barium carbonate.The carrier may be of any size or shape.

The annexed drawing shows, as an example, a glass carrier 3, which maybe of any shape. In the specific embodiment disclosed, the glass carrier3 is in the form of a block which has parallel planar faces 3a and 31).However, the carrier 3 may be of any shape, including a hollow or solidcylinder. The drawing is not to scale, as it is wholly diagrammatic.

A solid layer 4 of the radio-active material is deposited upon the face3a of the carrier 3. Said layer 4 may be an amalgam of the radioactivematerial.

As one example, the layer 4 may be a solid layer of radium bromide,which may contain some water, but is preferably wholly or substantiallyfree from water. I can use radium chloride, radium nitrate, radiumnitrite, radium perchlorate, etc. Whenever I refer to any substance orto other details, as part of a working example, the invention is notlimited thereto.

. I prefer to use radium salts which are soluble is not limited to theuse of a carrier which is made of glass, I prefer to use a carrier whichis made of glass, because the electrical resistance of glass diminishesrapidly with an increase in its temperature. Indeed, glass behavesalmost as an electrolyte, in that its resistance diminishes with a risein temperature, especially when the glass softens or begins to soften oris close to the softening temperature.

While the invention includes the use of any type or composition ofglass, I prefer to use a glass which has some conductivity at 20 C. Imay use the type of heat-resistant glass, which is a borosilicate glasswhich contains substantially no metals of the magnesia-lime-zinc groupand substantially no heavy metals. I can use the barium glasses. I canuse the type of heat-resistant glass which begins to soften at about 6000., especially if pressure is employed. I can use the type of glasswhich begins to soften under pressure at about 800 0.

Instead of glass, I can use other solid materials which have some degreeof electrolytic conductivity in the solid state at suitable elevatedtemperature. For example, I can use the halo.

in water, such .as radium bromide and radium chloride, but the inventionis not limited thereto. In order to form the layer 4, I can use eitheran aqueous solution of radium bromide, or I can use a solvent other thanwater. For example, I can use a solution of radium chloride in ethylalcohol.

For example, in order to form the layer 4, I can use a solution ofradium bromide in distilled watenin the proportion of one milligram ofradium bromide in 0.5 cc. of distilled water. This solution is appliedto the face 3a of the carrier 3. The solution may be applied totheentire face 3a, or to any selected part or parts thereof. Thesolution is applied, drop by drop,"

to the face 3a, or to any selected area or areas thereof. The carrier 3is preferably heated to about 50 C., before applying said solutionthereto. The solution may be confined in any suitable manner to theselected area or areas of the face 3a, until the solvent has evaporated.In order to evaporate the solvent rapidly, if said solvent is water, thecarrier 3 may be heated to about C. after the solution .has beenapplied, thus evaporating the water and providing a very thin layer 4.

The carrier 3 is now located between the electrodes I and 2. Theseelectrodes I and 2 may be made of any suitable conducting material. Inthe practical example whose details are stated herein, said electrodes Iand 2 can be made of pure nickel.

The electrodes I and 2 are applied respectively to the outer face of thelayer 4, and to the face 3b of the carrier 3, under suitable pressure,in order to secure good electrical contact. This pressure may be 500grams per square centimeter, or more. as is desired.

If the carrier 3 is made of material which has The pressuremay be ashigh low conductivity at normal temperature,- .s aid carrier is heatedto a suitable operating temperature in order to increase itsconductivity, pref erably before the electrodes I and 2 are applied.

although the carrier 3 may be heated, to the.

operating temperature, either wholly or partially, after the electrodesI and 2 are applied. The carrier 3 is heated to a temperature of about300 C.-800 0., depending upon the composition of the material of saidcarrier, if it is made of material which has low conductivity at normaltemperature. v

In-using reat-resistant glass, at suitable opere ating temperature isabout 500 C. to 600 C. At this operating temperature, the heat-resistantglass carrier 3 becomes sufficiently conductive so that current passesbetween the electrodes I and 2, through the solid layer 4 and throughthe carrier 3. Likewise, at said temperature of 500 C.. :600 C. theradio-active material can enter the carrier, to be incorporated in saidcar rier. The electrode I-is connected by a Wire 5 to the positiveterminal of a suitable source of constant and direct current and theelectrode 2 is connected by a wire 6 to the negative side of saidsource. The difference of voltage between the electrodes I and 2 can bebetween 500-1000 volts. The current through the layer 4 and the carrier3 can be about one milliampere', although it may be greater or less.

I do not exclude the use of a carrier 3 which has sufficientconductivity at ordinary temperatures of about C., such as certain typesof glass.

I prefer to use a constant unidirectional current. However, I can useother types of current, such as an intermittent-unidirectional current.I do not exclude the use of alternating current.

Under the action of the direct current to which-this working example isspecifically directed, the radio-active material migrates from the layer4 into the adjacent portion of the carrier 3. For most purposes, it issuflicient toincorporate a very small amount of the radioactive materialinto the carrier. In the practical example stated, the equivalent ofabout two milligrams of radium, as detected by radic activitymeasurement, is incorporated into the carrier 3 per square decimeter ofthe surface of the carrier.

If the carrier 3 is made of transparent glass,

it remains more or less transparent after the radio-active material hasbeen incorporated therein. In the practical example above given, inwhich the operating temperature was 500- 600 C., the passage ofa'curren-t of about one milliampere, under a voltage of about 500 volts,was continued for a period of about 30 minutes.

The radio-active material is sharply concentrated adjacent the face orwall 3a, which is a decided advantage in securing a maximum radio-activeeffect because the radiations, cs-

active material were exposed in a thin layer on said surface.Nevertheless, and as further stated herein, the incorporated radioactivematerial cannot be removed from the carrier, without removing thesurface material of the carrier. Glass can block the alpha rays, but Iprevent such blocking by incorporating radioactive material into thecarrier, very close to an exposed face of the carrier.

The. test of the finished product is the application' of a solvent forthe radio-active material, or subjecting the carrier 3 to some othertreatment which would ordinarily'removeithe radio-active material, if itwere not suitably-in:

corporated into the carrier 3. For example, after the radium has beensuitably incorporated into the heat-resistant carrier 3, according tothe practical example stated herein, the face 3a may be washed withwater or acids, without removing any of the radium.

.By continuing the passage of the current, the

' radium or other radio-active-material is carried further into thecarrier 3, away from the face 3a. The invention includes such extendedpassage of the current, although l'prefer'to concentrate the radioactivematerial in a selected volume of the carrier 3.

The impregnatedcarrier may be used for many purposes. The alpha or betaradiations vigor ously ionize the air adjacent the face 3a.; The

carrier 3 may therefore be used as a guide member over which a web ofpaper or cloth or the like can be guided, because the alpha or betaradiations will vigorously ionize the air, thus preventing the formationof static electricity which is frequently caused by friction. This'isparticularly valuable in many industries, especially in rotogravureprinting, in which the ink includes inflammable and volatile material.The face 3b can be fused or otherwise connected'to any suitable supportor member. For example, the face 31) can be fused to the interior wallof a tube which. contains a gas or gases, in" which it is desired toionize the gaseous filling. Said tube may be evacuated in order'toreduce the pressure therein to any desire low pressure. Said vacuum maybe very high. For convenience, the

' erasable markings which are made with compositions which include afluorescent, pigment or dye, such as calcium sulphide or rhodami ne 'B,so that said markings will be visible in darkness. These markings can bemade on a separate carrier, which can be applied to said face or faces.

Impregnated carriers of various sizes and shapes are also very usefulfor many medical purposes.

Atypical heat-resistant glass consists of 30.5 Of SiOz, 11.9% 01 B203,2% of A1203, 0.1% Of FezOs, 0.2% of (780, 0.2% of M90, 3.8% of NazO,0.6% Of K20, and 0.7% Of AS203, but I can use other types of Pyrex glassor other glass.

At the temperature and pressure utilized, the glass is preferably at thesoftening temperature, or close to said temperature. At the operatingtemperature which may be as high as 800 C., as above mentioned, theradium salt may be fused or unfused. For example, radium bromide has amelting point of 728 C., and radium chloride has a melting point ofabout 1000 C. However, the original shape of the glass carrier is notchanged by the incorporation of the radio-active material therein.

While no chemical combination is formed between the carrier and theradio-active material, the carrier is combined with the radio-activematerial, in the sense that said radio-active material is incorporatedinto the carrier.

I have described a preferred embodiment of my invention, but it is clearthat numerous changes and omissions can be made without departing fromits spirit.

I claim:

1. A method of incorporating radio-active material from an unfusedradium salt into a non-metallic and unfused carrier whose electricalresistance diminishes with rise in temperature, said carrier beingsubstantially free from radium, which consists in passing a currentthrough said unfused radium salt and through said unfused carrier whilesaid unfused salt contacts with said unfused carrier, said current'being passed through said unfused radium salt and through said unfusedcarrier at a temperature which is sufilciently elevated and under asufliciently high potential to pass a current through said unfused saltand said unfused carrier and to incorporate said radio-active materialinto said unfused carrier interiorly of the face of said unfused carrierwhich contacts with said unfused radium salt, said temperature andvoltage and the period of said incorporation being selected so that saidradio-active material is incorporated into said carrier so close to saidface that the alpha particles which are emitted by said incorporatedradio-active material pass out of said carrier; said carrier beingglass, said temperature being substantially 300 C.-800 0., said currentbeing unidirectional and its positive terminal being applied to saidradium salt, and its negative terminal being applied to said carrier,and the voltage of said current being substantially 500-1000 volts.

2. A method according to claim 1, said current being substantially onemilliampere.

3. A method according to claim 1, in which said radium salt is radiumbromide.

4. A method according to claim 1, in which said radium salt is radiumbromide, and said current is substantially one milliampere,

SOLOMON ROSENBLUM.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 821,655 Lieber May 29, 19061,210,731 Viol Jan, 2, 1917 1,644,370 Gaschler Oct, 4, 1927 1,832,607Zworykin Nov. 17, 1931 2,198,733 Leibig Apr, 30, 1940 FOREIGN PATENTSNumber Country Date 110,479 Australia May 9, 1940 278,347 Great BritainMay 10, 1928 OTHER REFERENCES Zeitschrift fur Physikalische Chemie, vol.A173, pages 321-344, (1935).

